1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device which takes into consideration variations in focus due to pressure changes, and also relates to an exposure system.
2. Description of the Related Art
A semiconductor manufacturing apparatus called an exposure apparatus is used in the photolithography process for manufacturing semiconductor devices. The exposure apparatus transfers a circuit pattern which is drawn on a photo mask onto a semiconductor wafer. There is constant demand for this circuit pattern to be miniaturized, and in response to this demand, there have been improvements in the exposure apparatus. However, the demand for miniaturization has been even more pressing in recent years. In order to form a miniaturized circuit pattern, control of the circuit pattern dimensions has become very strict. One factor which causes variation in the pattern dimensions is focus error in the exposure apparatus, or in other words defocusing.
In the exposure apparatus mechanism, the focus position varies due to pressure variations. Because of this, the exposure apparatus performs correction of the focus position in accordance with pressure (Jpn. Pat. Appln. KOKAI Publication No. 10-289865 publication). In the prior art, the defocus value is estimated assuming that the pressure and the focus position are proportional to each other, and defocus correction is performed based on the estimated defocus value. However, the details of the relationship between the pressure and the focus position are not known. Consequently, detailed focus correction cannot be performed in accordance with pressure variation, and thus defocusing sometimes occurs.
As described above, there is the problem that details of the relationship between the pressure and the focus position are not known, and thus the accuracy of the defocus value that is predicted from the pressure is low, and detailed focus correction based on the pressure cannot be performed.